Plasma arc torch systems can be applied to a wide variety of material processing applications such as cutting the thin plates of metal used for heating, ventilation and air conditioning systems or thick plates. Traditionally, plasma arc cutting systems are not portable because they require a large, cumbersome gas source (or a continuous, fixed gas source) and large amounts of power drawn from the electrical power grid via a corded attachment.
A plasma arc torch generally includes a torch body, an electrode mounted within the body, a nozzle with a central exit orifice, electrical connections, passages for cooling and arc control fluids, a swirl ring to control the fluid flow patterns, and a power supply. The torch produces a plasma arc, which is a constricted ionized jet of a plasma gas with high temperature and high momentum. Gases used in the torch can be non-reactive or reactive (e.g. argon, nitrogen, oxygen or air).
In operation, a pilot arc is first generated between the electrode (cathode) and the nozzle (anode). The pilot arc ionizes gas passing through the nozzle exit orifice. After the ionized gas reduces the electrical resistance between the electrode and the workpiece sufficiently, the arc transfers from the nozzle to the workpiece. The torch may be operated in this transferred plasma arc mode, which is characterized by the conductive flow of ionized gas from the electrode to the workpiece, for the cutting of the workpiece.
Despite cordless power tools being pervasive in the commercial market, plasma arc torch systems have yet to be efficiently adapted for easy, portable usage. One design difficulty is caused by the relatively large gas consumption of a plasma arc torch. Another design difficulty is caused by the high power requirements of the plasma arc torch system, e.g., about 1.32 kW output for a low power system such as the Powermax™ 190C manufactured by Hypertherm, Inc. of Hanover, N.H.; 8.4 kW output for a medium power torch system such as the Powermax 1000 manufactured by Hypertherm and up to 16,000 kW output for a high power torch system such as the Powermax 1650 manufactured by Hypertherm. The high power requirements of a plasma arc torch system have resulted in designs where the plasma arc torch system is used by plugging into a wall, utilizing a continuous supply of AC power. There exists a difficult balance between the performance of the torch, the lifetime of the gas and power sources, and actual physical size of the plasma arc torch system.
It is therefore desirable to provide a portable plasma arc cutting system that has power considerations for operating the torch effectively at lower gas consumption and lower power levels, while providing portability and performance for the applications described above. Additionally, it is desirable for the gas and power sources of the plasma arc torch system to operate for a commercially useful duration with ease of recharge or replacement for repeatable use.